大腸桿菌藉由ArsA蛋白使其對砷化物產生抗性。利用序列分析釀酒酵母Saccharomyces cerevisiae，發現YDL100c轉譯的yArsA與大腸桿菌ArsA具有同源性，殊不知yArsA在酵母細胞內所扮演的角色。YDL100c的缺失對於酵母細胞並非致死因素，卻降低酵母細胞對熱的耐受程度。
為了研究yArsA在釀酒酵母對熱耐性所扮演的角色，本實驗將野生株(WT)及突變株(KO)培養於25℃和37℃，並針對細胞內的自由基清除系統、trehalose的累積以及熱休克蛋白的誘導做分析。初步實驗結果證明：在37℃時，KO菌株的細胞內分子氧化程度較WT菌株為高，而其trehalose的含量則較WT菌株低，ROS的增加以及trehalose含量的減少是導致KO菌株細胞死亡的原因。利用RT-PCR分析自由基清除系統相關基因的mRNA表現量，結果指出在25℃或37℃下的WT和KO菌株，其TSL1及SOD1的表現並無顯著差異；而在37℃下，KO菌株的CTT1表現量則明顯低於WT 菌株。針對CTT1轉譯的catalase做酵素活性分析，在37℃時，KO菌株的catalase活性亦明顯較WT菌株低。Catalase活性的下降，trehalose含量的減少以及Hsp104p表現量較低等現象指出KO菌株在37℃下調控general stress response活化的缺失。本實驗證實yArsA在釀酒酵母面對stress的情況下，參與細胞內general stress response pathway的調控。

The E. coli ArsA is involved in arsenic detoxification but the role of yArsA (ArsA homologue of Saccharomyces cerevisiae, encoded by YDL100c ORF) in yeast is still undefined. Disruption of YDL100c ORF is not lethal but the disrupted strain (KO) shows decreased thermotolerance.
To study the role of yArsA in thermotolerance, wild type (WT) and KO were grown at 25℃and 37℃, and assayed for the intracellular levels of trehalose accumulation and molecular oxidation, and the biosynthesis of heat shock proteins. The results show that molecular oxidation is higher and trehalose accumulation is lower in KO compared with WT grown at 37℃, suggesting that increased ROS and decreased trehalose content are the cause of cell death. Further analysis of the expression of ROS defense mechanisms show that there is no significant difference in TSL1 and SOD1 expression in WT and KO grown at 25℃ or 37℃ but the CTT1 expression in KO was much less than WT grown at 37℃. These observations are consistent with the assays of enzymatic activity of catalase and antioxidant GSH contents. Loss of catalase activity, decreased trehalose contents and Hsp104p expression suggest a deficiency in activation of general but not specific stress response in KO when grown at 37℃. Therefore, yArsA was involved in signaling the general stress response in stress tolerance network.

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Materials and Methods-----------------------------------------------------------------------11
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